With the expanding use of computers in widely varied environments, and more significantly the increasing size of software programs and data files that are employed on those computers, the dissemination of computer software is becoming significantly more complex. Originally, when software programs and data files were of relatively small size, distribution of the programs and files by means of floppy disks was feasible. However, as the processing power of computers continues to expand, and internal storage media such as hard disks offer greater capacity, there is a tendency for software programs to become larger in size. Concomitantly, data files which are processed by those programs, particularly files relating to images and other graphics, have also increased in size. As a result, floppy disks no longer offer a convenient medium for distributing electronic data, due to their limited storage capacity. While a user may be quite willing to install a new software program that is contained on a few floppy disks, the time and effort required to install a large program that occupies a significant number of disks to store all of its contents, e.g., 20 or more disks, becomes intolerable.
For this reason, other media having larger storage capacity, such as CD ROMs, have been employed more recently for the distribution of larger amounts of software. While these other types of media decrease the time and effort required to install the software, they still have certain limitations associated with them. For example, the need to separately package and ship each CD ROM, or the like, requires an appreciable amount of overhead on the part of the software manufacturer. In addition, the storage of the media, both at retail outlets and at the end user's site, represents a growing burden as the number of programs and data files continues to expand.
To overcome these limitations associated with the limited size of transportable storage media and the need to accommodate or dispose of the media, it is desirable to distribute software, including both programs and data files, in an electronic format. Currently, installer programs are available which provide a user with an opportunity to install a program on a computer from a remote site. In one type of installer, a large number of bundled files are downloaded from the remote site in a compressed format, and then expanded on the user's computer. From this large number of files, the user picks the few that are desired, and they are installed on the user's computer system. From the standpoint of user convenience, this approach is less than ideal, because of the time spent downloading a number of unnecessary files, as well as the effort required by the user to select the needed files. In contrast to this approach, a "one-button" installation system is preferable. In such an approach, the user is only required to perform a single action, e.g., select a single button in a graphical user interface, to have the appropriate files downloaded and installed.
Typically, in a one-button installer, all required files are compressed into a single file known as a "tome." The tome is provided together with an installer program and a script file that is downloaded to the user's site. The installer program, together with the information contained in the script file, expands the tome back into the individual files, and installs the files onto the user's computer system. To perform the installation, the user is only required to select the installer program to run. All other actions are carried out automatically thereafter.
While the latter approach offers the convenience of a one-button installation system, to date it has been limited in the types of programs with which it can be employed. More specifically, due to restrictions associated with the number of resources that can be handled in a tome, it is not possible to use the one-button installer system for programs having large files, or a large number of files, such as operating system software.
Furthermore, since installer programs operate on files individually, they are not able to ensure the integrity of files installed on the user's system. More particularly, since each individual file is compressed and expanded during the installation process, it is not possible to provide end-to-end verification of each file. For example, the original file may have a checksum value tagged to it, to provide for verification of the integrity of the file when it is copied. However, as part of the process of compressing the file, the checksum value is not always preserved. For example, the file might be renamed. Consequently, when the file is expanded and installed, it is not impossible to employ the checksum value to verify the integrity of the file.